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            <small>
              <a href="#Procedure">Procedure<br></a>
              <a href="#Abstract">Abstract<br></a>
              <a href="#Required_Reading">Required_Reading<br></a>
              <a href="#Keywords">Keywords<br></a>
              <a href="#Brief_I/O">Brief_I/O<br></a>
              <a href="#Detailed_Input">Detailed_Input<br></a>

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              <small>               <a href="#Detailed_Output">Detailed_Output<br></a>
              <a href="#Parameters">Parameters<br></a>
              <a href="#Exceptions">Exceptions<br></a>
              <a href="#Files">Files<br></a>
              <a href="#Particulars">Particulars<br></a>
              <a href="#Examples">Examples<br></a>

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              <small>               <a href="#Restrictions">Restrictions<br></a>
              <a href="#Literature_References">Literature_References<br></a>
              <a href="#Author_and_Institution">Author_and_Institution<br></a>
              <a href="#Version">Version<br></a>
              <a href="#Index_Entries">Index_Entries<br></a>
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<h4><a name="Procedure">Procedure</a></h4>
<PRE>
   void swpool_c ( ConstSpiceChar    * agent,
                   SpiceInt            nnames,
                   SpiceInt            lenvals,
                   const void        * names   ) 
</PRE>
<h4><a name="Abstract">Abstract</a></h4>
<PRE>
 
   Add a name to the list of agents to notify whenever a member of 
   a list of kernel variables is updated. 
 </PRE>
<h4><a name="Required_Reading">Required_Reading</a></h4>
<PRE>
 
   <a href="../req/kernel.html">KERNEL</a> 
 </PRE>
<h4><a name="Keywords">Keywords</a></h4>
<PRE>
 
   CONSTANTS 
   FILES 
 

</PRE>
<h4><a name="Brief_I/O">Brief_I/O</a></h4>
<PRE>
 
   VARIABLE  I/O  DESCRIPTION 
   --------  ---  -------------------------------------------------- 
   agent      I   The name of an agent to be notified after updates. 
   nnames     I   The number of variables to associate with agent. 
   lenvals    I   Length of strings in the names array.
   names      I   Variable names whose update causes the notice. 
 </PRE>
<h4><a name="Detailed_Input">Detailed_Input</a></h4>
<PRE>
 
   agent       is the name of a routine or entry point (agency) that 
               will want to know when a some variables in the kernel 
               pool have been updated. 
 
   nnames      is the number of kernel pool variable names that will 
               be associated with agent. 
 
   lenvals     is the length of the strings in the array names, 
               including the null terminators.  
              
   names       is an array of names of variables in the kernel pool. 
               Whenever any of these is updated, a notice will be 
               posted for agent so that one can quickly check 
               whether needed data has been modified. 
 </PRE>
<h4><a name="Detailed_Output">Detailed_Output</a></h4>
<PRE>
 
   None. 
 </PRE>
<h4><a name="Parameters">Parameters</a></h4>
<PRE>
 
   None. 
 </PRE>
<h4><a name="Exceptions">Exceptions</a></h4>
<PRE>
 
   1) If sufficient room is not available to hold a name or new agent,
      a routine in the call tree for this routine will signal an error.
 
   2) If either of the input string pointers are null, the error 
      SPICE(NULLPOINTER) will be signaled.
      
   3) If any input string agent has length zero, the error 
      SPICE(EMPTYSTRING) will be signaled.
      
   4) The caller must pass a value indicating the length of the strings
      in the names array.  If this value is not at least 2, the error
      SPICE(STRINGTOOSHORT) will be signaled.
      </PRE>
<h4><a name="Files">Files</a></h4>
<PRE>
 
   None. 
 </PRE>
<h4><a name="Particulars">Particulars</a></h4>
<PRE>
 
   The kernel pool is a convenient place to store a wide variety of
   data needed by routines in CSPICE and routines that interface with
   CSPICE routines.  However, when a single name has a large quantity
   of data associated with it, it becomes inefficient to constantly
   query the kernel pool for values that are not updated on a frequent
   basis.
 
   This entry point allows a routine to instruct the kernel pool to
   post a message whenever a particular value gets updated. In this
   way, a routine can quickly determine whether or not data it requires
   has been updated since the last time the data was accessed.  This
   makes it reasonable to buffer the data in local storage and update
   it only when a variable in the kernel pool that affects this data
   has been updated.
 
   Note that <b>swpool_c</b> has a side effect.  Whenever a call to <b>swpool_c</b>
   is made, the agent specified in the calling sequence is added to the
   list of agents that should be notified that an update of its
   variables has occurred.  In other words the code
 
       <b>swpool_c</b> ( agent, nnames, lenvals, names   ); 
       <a href="cvpool_c.html">cvpool_c</a> ( agent,                  &amp;update ); 
 
   will always return update as SPICETRUE. 
 
   This feature allows for a slightly cleaner use of <b>swpool_c</b> and
   <a href="cvpool_c.html">cvpool_c</a> as shown in the example below.  Because <b>swpool_c</b>
   automatically loads agent into the list of agents to notify of a
   kernel pool update, you do not have to include the code for fetching
   the initial values of the kernel variables in the initialization
   portion of a subroutine.  Instead, the code for the first fetch from
   the pool is the same as the code for fetching when the pool is
   updated.
 </PRE>
<h4><a name="Examples">Examples</a></h4>
<PRE>
 
   Suppose that you have an application subroutine, MYTASK, that 
   needs to access a large data set in the kernel pool.  If this 
   data could be kept in local storage and kernel pool queries 
   performed only when the data in the kernel pool has been 
   updated, the routine can perform much more efficiently. 
 
   The code fragment below illustrates how you might make use of this 
   feature. 
 
      #include &quot;SpiceUsr.h&quot;
           .
           .
           .
      /.  
      On the first call to this routine establish those variables 
      that we will want to read from the kernel pool only when 
      new values have been assigned. 
      ./
      if ( first )
      {
         first = SPICEFALSE;
         <b>swpool_c</b> ( &quot;MYTASK&quot;, nnames, lenvals, names ); 
      }
 
      /.
      If any of the variables has been updated, fetch them from the
      kernel pool.
      ./    
        
      <a href="cvpool_c.html">cvpool_c</a> ( &quot;MYTASK&quot;, &amp;update ); 
 
      if ( update )
      {
         for ( i = 0;  i &lt; NVAR;  i++ )
         {
            <a href="gdpool_c.html">gdpool_c</a>( MYTASK_VAR[i], 1, NMAX, n[i], val[i], &amp;found[i] );
         }
      }
 
 </PRE>
<h4><a name="Restrictions">Restrictions</a></h4>
<PRE>
 
   None. 
 </PRE>
<h4><a name="Literature_References">Literature_References</a></h4>
<PRE>
 
   None. 
 </PRE>
<h4><a name="Author_and_Institution">Author_and_Institution</a></h4>
<PRE>
 
   N.J. Bachman    (JPL)
   W.L. Taber      (JPL) 
 </PRE>
<h4><a name="Version">Version</a></h4>
<PRE>
 
   -CSPICE Version 1.3.0, 27-AUG-2002 (NJB)

      Call to C2F_CreateStrArr_Sig replaced with call to C2F_MapStrArr.

   -CSPICE Version 1.2.0, 28-AUG-2001 (NJB)

      Const-qualified input array names.

   -CSPICE Version 1.1.0, 14-FEB-2000 (NJB)

       Calls to C2F_CreateStrArr replaced with calls to error-signaling 
       version of this routine:  C2F_CreateStrArr_Sig.
      
   -CSPICE Version 1.0.0, 05-JUN-1999 (NJB) (WLT)
</PRE>
<h4><a name="Index_Entries">Index_Entries</a></h4>
<PRE>
 
   Watch for an update to a kernel pool variable 
   Notify a routine of an update to a kernel pool variable </PRE>
<h4>Link to routine swpool_c source file <a href='../../../src/cspice/swpool_c.c'>swpool_c.c</a> </h4>

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   <pre>Wed Jun  9 13:05:31 2010</pre>

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